Prior exposure to ozone potentiates subsequent response to sulfur dioxide in adolescent asthmatic subjects.
The objective of this study was to test whether prior exposure to a low concentration of ozone (120 ppb) would condition airways in asthmatic subjects to respond to a subthreshold concentration of sulfur dioxide (100 ppb). Eight male and five female subjects 12 to 18 yr of age participated. They all had allergic asthma and exercise-induced bronchospasm. Subjects were exposed to three test atmosphere sequences during intermittent moderate exercise (a 45-min exposure to one pollutant followed by a 15-min exposure to the second pollutant). The sequences were: air followed by 100 ppb SO2, 120 ppb O3 followed by 120 ppb O3, and 120 ppb O3 followed by 100 ppb SO2. The pulmonary function measurements assessed were FEV1, total respiratory resistance (RT), and maximal flow (Vmax50). Air-SO2 and O3-O3 exposures did not cause significant changes in pulmonary function. On the other hand, exposure to 100 ppb SO2 after a 45-min exposure to 120 ppb O3 caused a significant (8%) decrease in FEV1 (p = 0.046), a significant (19%) increase in RT (p = 0.048), and a significant (15%) decrease in Vmax50 (p = 0.008). It is concluded that prior O3 exposure increased bronchial hyperresponsiveness in these subjects such that they responded to an ordinarily subthreshold concentration of SO2. These data suggest that assessment of pulmonary changes to single pollutant challenges overlooks the interactive effects of common coexisting or sequentially occurring air pollutants.
Koenig
J Q
JQ
Department of Environmental Health, University of Washington, Seattle 98195.
Covert
D S
DS
Hanley
Q S
QS
van Belle
G
G
Pierson
W E
WE
D000293:Adolescent; D000393:Air Pollutants / Q000009:adverse effects*; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D001249:Asthma / Q000139:chemically induced* / Q000503:physiopathology; D001250:Asthma, Exercise-Induced / Q000139:chemically induced / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008448:Maximal Expiratory Flow Rate / Q000187:drug effects / Q000502:physiology; D010126:Ozone / Q000008:administration & dosage / Q000009:adverse effects*; D013458:Sulfur Dioxide / Q000008:administration & dosage / Q000009:adverse effects*; D013997:Time Factors
D000393:Air Pollutants; D013458:Sulfur Dioxide; D010126:Ozone